Sony Ericsson has used the Mobile World Congress to unveil two new tiny cell phones that run the Android operating system. Their names are the Xperia X10 mini and the X10 mini pro. Both are compact versions of the Xperia X10.

The main difference between the two handsets is the inclusion of a slide-out QWERTY keyboard. As you may have guessed the X10 mini pro is the one with the keyboard, the X10 mini just has a touchscreen.

Both share the following features:

UX platform/skin running on top of Android 1.6

Customizable home screen touchscreen corners for widgets

5-megapixel camera

Sony Ericsson Timescape application

2.55″ touchscreen

Interactive music player with “infinite button”

3.5mm headphone jack, Bluetooth connectivity and GPS functionality

2GB MicroSD card included in the box

The customizable home screen will allow the user to select which widgets are most accessible on their phone. That includes any applications downloaded from the Android Market or existing apps included with the phone.

The Timescape app is meant to bring together all the information important to a user on one place. So any phone calls, texts, Twitter, or Facebook updates should all be accessible from Timescape. Music also seems to be a major feature on both devices and the “infinite button” can apparently, “pull together all music content from the music store and YouTube”.

The X10 mini will be available in black, pearl white, lime, pink, red, and silver, while the pro is limited to black and red. Both handsets are expected to be available in the second quarter of this year, but in which markets has yet to be announced.

As far as I can tell Sony Ericsson has attempted to make both phones look the same with the exception of one having a keyboard. Surprisingly that only makes it 2mm thicker; so for me having the keyboard option is worth it.

I’ve included an image of each above, but Pocket-lint has 40 pictures if you want a better look at both devices.

If portability is a major concern for you, and you also want Android, then both of these phones may be a nice solution. The Nexus One and other HTC Android phones in genral are quite large where as these X10 models are tiny. The sacrifice you make for the smaller handset is usability. Some functions, such as web browsing, will probably be less than great on an X10 mini when compared to a Droid or Nexus One.